Adding a 2nd Server to a domain that has no real DNS name

I'm having a first W2003 Server that is a Domain Controller in a Active Directory environment.
The domain is called vanlier.be, although we have that domain for email purposes we have no website behind it. There is no need to do so. The first server is also running a DNS server. It has a fix ip adress and 2 real DNS server configured from our ISP. All computer/server go on the net by a DSL Router.
When trying to activate the Active directory on the second W2003 Server, adding it to an existing domain i must key in user/password and domain. When keying in vanlier.be i'm getting the messages that the domain is not found, and has been checked by the 3 DNS servers (the 2nd machine also has the 2ISP DNS servers and the ip of the 1st ActDir DomContr.
Any suggestions on how to get passed this name, and what to do to get it right.
Kind Regards
Harry

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Also make sure that all the servers are pointing to internal DNS servers only. The Domain controller should be pointing to itself and the client machines (including this new server) should be pointing to the DC. No external DNS servers should be entered on any of the machines.

DO you have a DNS zone for vanlier.be hosted LOCALLY? if it is elsewhere (this is how it sounds) then DCPROMO will fail - Active directory needs to have access locally to a DNS namespace that is THE SAME as the active directory name :)

All servers no longer point to external DNS servers, only the internal DNS server (same as 1st Domain Controller) is in the DNS list.
When i ping a www.yahoo.com it still is working, so that works fine.
But, when adding the 2nd server to the domain it still doesn't work.
I supose thet there is something wrong with my forward lookup zones.
I created one named 'vanlier.be', i supose that just not the name that had to be chosen as the vanlier.be should be locally, but what other name should i put there so that all other dns-request are forwarded.

BTW, Thx for both the answers, i'm new to exp-xchange and find it quite hard that i only can 'reward' one person, although both of you made the effort of answering.